The present invention relates to a paving stone or ground covering stone of the type in which free spaces of considerable size for discharging water are left between mutually identical paving stones that are laid beside each other on a ground. The paving stone consists preferably of concrete.
In the past few years one could note a tendency towards the increasing use of paving stones for paving areas, such as pedestrian areas, yards, squares, garage drives, footpaths, factory yards, port installations etc. The ground areas paved with paving stones laid thereon, which are in particular artificial paving stones of concrete, present a clean, neat and optically pleasing appearance and are well suited for being driven on by vehicles and for being used by pedestrians. However, the increasing use of paving stones entails a certain occlusion of the ground with respect to rainwater. Rain is then discharged into the ground only to a small degree through the gaps between adjacent paving stones, whereas most of the rainwater flows off over the paved area and is discharged into a drainage system. Consequently, this extensive occlusion of areas leads to an increased amount of water for the drainage system and sewage plants and moreover to increased lowering of the groundwater level as compared with the condition without stone pavement. However, it is generally desired not to have the groundwater level drop excessively, in particular in order to maintain the important humidity reservoir of the groundwater for the roots of trees and for rendering the winning of drinking water from groundwater easier.
For mitigating the above-mentioned disadvantageous consequences of paving areas with paving stones, it has already been conceived to provide water discharge spaces between adjacent paving stones, so that more water flows into the ground and is not discharged into the drainage system. A first known approach for achieving this consists in the provision of local spacing projections so that relatively wide downwardly opening gaps result between adjacent paving stones. A typical example of this prior art is German-"Offenlegungsschrift" No. 33 03 225. A second approach for providing ground pavements of paving stones that permit the passage of more water consists in providing, at specific locations of the outline of the particular paving stone, a recess that is not filled when placing a neighboring paving stone adjacent thereto, so that local free spaces for discharging precipitation result in the finished pavement. A typical example of this prior art is German Utility Model No. 78 21 651.
Furthermore, U.S. Pat. No. 4,128,357 to Barth et al shows a paving stone in which a first part, having the configuration of a centrally symmetrical octagon, and a second part, having the configuration of a square with four protrusions projecting outwardly at the corners at an angle of 45.degree., are integrally joined together and are optically separated from one another by a dummy gap or dummy groove. When laying a plurality of these known paving stones beside each other, the paved area is occluded completely except for the relatively narrow gaps between the paving stones. Thus, free spaces for the discharge of water into the ground are not provided.